This invention relates to planar coil configurations and more particularly to such structure employed as a rotary displacement sensor.
There is a need for rotary sensors which are capable of providing an output according to a selected angle of rotation. The prior art shows many such devices but there does not exist such a sensor or transducer that is inexpensive and is capable of a wide range of operation. In most prior art sensors great difficulty is encountered in traversing a large angular range. There are sensors which will provide sine or cosine waveforms but these are relatively expensive and very complicated.
The concept of using planar coil configurations to provide sensor operation as to convert linear or rotary motion to an electrical output signal has been described in my copending application entitled PLANAR COIL APPARATUS FOR PROVIDING MOTION SENSORS, SWITCHES AND VARIOUS STRUCTURES filed on Dec. 8, 1980 as Ser. No. 214,725, now abandoned. In this application, two planar coil members are positioned one above the other in a parallel plane to provide a space between the members. A ferromagnetic coupling member is movably, positioned in the space to thereby allow a magnetic filed induced in one coil to couple to the other coil when the member is moved out of the space and to prevent coupling of the magnetic field when the member is disposed within the space. As explained in that application, the planar coil configuration offers great advantages in regard to providing inexpensive and reliable transducer operation.
The concept of using planar coils has also been described in my copending application entitled PLANAR COIL APPARATUS EMPLOYING A STATIONARY AND A MOVABLE BOARD filed on Feb. 9, 1981 as Ser. No. 232,654, now U.S. Pat. No. 4,425,511. In this application a first stationary planar coil is located adjacent to another planar coil which may be fabricated on the same circuit board. A drive signal is applied to the input terminals of one of the coils. A second planar board is positioned above the first board and has located thereon a planar coil configuration which constitutes a closed loop. This board is moved with respect to the stationary board and magnetic flux is coupled via the closed loop from the drive coil to the other coil which is defined as a sense coil. In this configuration by monitoring the output of the sense coil a signal can be detected indicative of the distance that the movable board traversed. Therefore these sensors provide a signal indicative of the distance moved.
As is known, prior art devices which operate as sensors may be variable resistance elements such as those used in displacement transducers as well as other sensing devices which are inductive or capacitive devices. These prior art devices are extremely expensive to manufacture and less reliable than the type of sensors using planar coils as above described.
U.S. Pat. No. 4,253,079 issued on Feb. 24, 1981 entitled DISPLACEMENT TRANSDUCERS EMPLOYING PRINTED COIL STRUCTURES by Amnon Brosh, the inventor herein disclosed the displacement transducer which includes a plurality of planar coil structures. The structures are located on separate planar boards each of which have a central aperture and are positioned in a stacked array separate from one another. A magnetic member is inserted into the aligned apertures to vary the coupling between the coils. Thus this Patent which was awarded to the inventor herein depicts the use of planar coil configuration employed in a displacement transducer.
This application involves analog sensors and relates to the fabrication and construction of a rotary sensor structure utilizing planar coils. The structure to be described is extremely simple to construct while being reliable in operation. By using such a device one can provide electrical output signals which are indicative of angular movement over a wide range of angular positions as well as providing output waveforms which are proportional to sine or cosine functions. The apparatus to be described is extremely compact and simple to construct.